Compound, resin and photoresist composition

ABSTRACT

A resin comprising a structural unit represented by formula (I0): 
     
       
         
         
             
             
         
       
         
         wherein A 1 , A 2  and A 3  each independently represent a C2-C18 divalent hydrocarbon group, 
         R 1 , R 2 , R 3  and R 4  each independently represent a hydrogen atom or a C1-C6 saturated hydrocarbon group, 
         X 1  and X 2  each independently represent *—O—CO—, —O—CO—O— or —O—, and * represents a binding site to A 2  or A 3 .

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2016-149451 filed in JAPAN on Jul. 29, 2016,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to a compound, a resin and a photoresistcomposition and a process for producing a photoresist pattern.

BACKGROUND ART

JP2009-42748A1 mentions a resin obtained by polymerizing a compound ofthe following formula, and a photoresist composition comprising theresin and an acid generator.

SUMMARY OF THE INVENTION

The invention of the disclosure relates to the followings:

<1> A resin comprising a structural unit represented by formula (I0):

wherein A¹, A² and A³ each independently represent a C2-C18 divalenthydrocarbon group,

R¹, R², R³ and R⁴ each independently represent a hydrogen atom or aC1-C6 saturated hydrocarbon group,

X¹ and X² each independently represent *—O—CO—, —O—CO—O— or —O—, and *represents a binding site to A² or A³.

<2> The resin according to <1>,

wherein X¹ and X² each independently represent —O—CO—O— or —O—.

<3> The resin according to <1> or <2>,

wherein each of X¹ and X² represent —O—.

<4> The resin according to any one of <1> to <3>,

wherein A¹ represents a C2-C18 divalent aliphatic hydrocarbon group.

<5> The resin according to any one of <1> to <4>,

which further comprises a structural unit having an acid-labile group.

<6> The resin according to any one of <1> to <5>,

which further comprises a structural unit having a lactone ring.

<7> A photoresist composition which comprises the resin according to anyone of <1> to <6> and an acid generator.

<8> The photoresist composition according to <7>, further comprising aresin which comprises a structural unit having a fluorine atom.

<9> A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

(1) a step of applying the photoresist composition according to <7> or<8> on a substrate,

(2) a step of forming a composition film by drying the composition,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film.

<10> A compound represented by formula (I):

wherein A¹¹, A¹² and A¹³ each independently represent a C2-C18 divalenthydrocarbon group,

R¹¹, R¹², R¹³ and R¹⁴ each independently represent a hydrogen atom or aC1-C6 saturated hydrocarbon group,

X¹¹ and X¹² each independently represent *—O—CO—, —O—CO—O— or —O—, and *represents a binding site to A¹² or A¹³.

DESCRIPTION OF EMBODIMENTS

In the specification, “(meth)acrylate” and “(meth)acrylic acid” mean “anacrylate ormethacrylate” and “an acrylic acid or methacrylic acid,”respectively. Herein, chain structure groups include those having alinear structure and those having a branched structure.

The indefinite articles “a” and “an” are taken as the same meaning as“one or more”.

The term “solid components” means components other than solvents in aphotoresist composition.

<Resin>

The resin of the disclosure, which is sometimes referred to as “Resin(A)”, has a structural unit represented by formula (I0):

in which A¹, A² and A³ each independently represent a C2-C18 divalenthydrocarbon group,

R¹, R², R³ and R⁴ each independently represent a hydrogen atom or aC1-C6 saturated hydrocarbon group,

X¹ and X² each independently represent *—O—CO—, —O—CO—O— or —O—, and *represents a binding site to A² or A³.

The structural unit represented by formula (I0) is sometimes referred toas “structural unit (I0)”.

For A¹, A² and A³, examples of the divalent hydrocarbon group include adivalent aliphatic hydrocarbon group and divalent aromatic hydrocarbongroups, and any combination of these groups. Examples of the divalentaliphatic hydrocarbon group include an alkanediyl group, and amonocyclic or polycyclic divalent alicyclic hydrocarbon group.

Specific examples of A¹, A² and A³ include a linear alkanediyl groupsuch as an ethylene group, a propane-1,3-diyl group, a butane-1,4-diylgroup, a pentane-1,5-diyl group, a hexane-1,6-diyl group, aheptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diylgroup, a decane-1,10-diyl group, an undecane-1,11-diyl group and adodecane-1,12-diyl group;

a branched alkanediyl group such as a ethane-1,1-diyl group, apropane-1,2-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;

a monocyclic divalent alicyclic hydrocarbon group such ascycloalkanediyl group including a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,2-diyl group, a1-methylcyclohexane-1,2-diyl group, a cyclohexane-1,4-diyl group, acyclooctane-1,2-diyl group and a cyclooctane-1,5-diyl group;

and a polycyclic divalent alicyclic hydrocarbon group such as anorbornane-2,3-diyl group, a norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,5-diyl group and anadamantane-2,6-diyl group; and

divalent aromatic hydrocarbon group such as a phenylene group, anaphtylene group, a phenanthryl group, an anthrylene group, ap-methylphenylene group, a p-tert-butylphenylene group, ap-adamantylphenylene group, a tolyl group, a xylylene group, acumenylene group, a mesitylene group, a biphenylene group, aphenanthrylene group, a 2,6-diethylphenylene group, and a2-methyl-6-ethylphenylene group.

A¹ represents preferably a C2-C18 divalent aliphatic hydrocarbon group,more preferably a C2-C8 alkanediyl group, a C5-C10 divalent alicyclichydrocarbon group, and a divalent hydrocarbon group consisting of aC2-C8 alkanediyl group and a C5-C10 divalent alicyclic hydrocarbongroup, and still more preferably a divalent hydrocarbon group consistingof a C2-C4 alkanediyl group and a C5-C10 divalent alicyclic hydrocarbongroup. The divalent alicyclic hydrocarbon group for A¹ preferablyincludes a cycloalkanediyl group including a cyclobutanediyl group, acyclopentanediyl group and a cyclohexanediyl group.

Preferably, A² and A³ each independently represent a C2-C4 alkanediylgroup.

For R¹, R², R³ and R⁴, examples of the saturated hydrocarbon groupinclude alkyl groups such as a methyl group, an ethyl group, a propylgroup, a butyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, a pentyl group and a hexyl group; cycloalkyl groups such as acyclopentyl group and a cyclohexyl group, and any combination of thesegroups.

Each of R¹ and R² is preferably a hydrogen atom, a methyl group, or anethyl group, more preferably a hydrogen atom or a methyl group. Stillmore preferably, one of R¹ and R² is preferably a hydrogen atom, and theother is a methyl group.

Each of R³ and R⁴ is preferably a hydrogen atom, a methyl group, or anethyl group, more preferably a hydrogen atom or a methyl group. Stillmore preferably, one of R³ and R⁴ is preferably a hydrogen atom, and theother is a methyl group.

Preferably, X¹ and X² each independently represent —O—CO—O— or —O—.

More preferably X¹ represents the same group as X². Still morepreferably X¹ and X² are —O—.

Examples of the structural unit (I0) include the following ones. Amongthem, the structural units represented by formulae (I0-1) to (I0-4) arepreferred.

The structural unit (I0) is derived from a compound represented byformula (I):

in which A¹¹, A¹² and A¹³ each independently represent a C2-C18 divalenthydrocarbon group,

R¹¹, R¹², R¹³ and R¹⁴ each independently represent a hydrogen atom or aC1-C6 saturated hydrocarbon group,

X¹¹ and X¹² each independently represent *—O—CO—, —O—CO—O— or —O—, and *represents a binding site to A¹² or A¹³.

The compound represented by formula (I) is sometimes referred to as“compound (I)”.

Examples of A¹¹, A¹² and A¹³ include the divalent hydrocarbon groupsrepresented by A¹, A² and A³.

Examples of the saturated hydrocarbon group represented by R¹¹,

R¹², R¹³ and R¹⁴ include the saturated hydrocarbon group represented byR¹, R², R³ and R⁴.

A¹¹ represents preferably a C2-C18 divalent aliphatic hydrocarbon group,more preferably a C2-C8 alkanediyl group, a C5-C10 divalent alicyclichydrocarbon group, and a divalent hydrocarbon group consisting of aC2-C8 alkanediyl group and a C5-C10 divalent alicyclic hydrocarbongroup, and still more preferably a divalent hydrocarbon group consistingof a C2-C4 alkanediyl group and a C5-C10 divalent alicyclic hydrocarbongroup. The divalent alicyclic hydrocarbon group for A¹¹ preferablyincludes a cycloalkanediyl group including a cyclobutanediyl group, acyclopentanediyl group and a cyclohexanediyl group.

Preferably, A¹² and A¹³ each independently represent a C2-C4 alkanediylgroup.

Each of R¹¹ and R¹² is preferably a hydrogen atom, a methyl group, or anethyl group, more preferably a hydrogen atom or a methyl group. Stillmore preferably, one of R¹¹ and R¹² is preferably a hydrogen atom, andthe other is a methyl group.

Each of R¹³ and R¹⁴ is preferably a hydrogen atom, a methyl group, or anethyl group, more preferably a hydrogen atom or a methyl group. Stillmore preferably, one of R¹³ and R¹⁴ is preferably a hydrogen atom, andthe other is a methyl group.

Preferably X¹¹ and X¹² represent —O—CO—O— or —O—.

More preferably X¹¹ represents the same group as X¹². Still morepreferably X¹¹ and X¹² are —O—.

Examples of the structural unit (I) include the following ones.

The compound (I) can be produced by reacting the compound represented bythe formula (I-a), in the presence of a base such as sodium hydroxide,in a solvent such as methanol:

in which R¹¹, R¹², R¹³, R¹⁴, A¹¹, A¹² and A¹³ are as defined above. Thereaction can be conducted at temperature of preferably 5° C. to 60° C.,for 0.5 to 24 hours.

The compound represented by formula (I-a) can be obtained by reactingthe compound of the formula (I-b) and the compound of the formula (I-c)in a solvent such as dimethylformamide:

in which R¹¹, R¹², R¹³, R¹⁴, A¹¹, A¹² and A¹¹ are as defined above. Thereaction can be conducted at temperature of preferably 5° C. to 60° C.,for 0.5 to 24 hours.

The compound represented by formula (I-b) can be obtained by reactingthe compound of the formula (I-d) and the compound of the formula (I-e)in the presence of an acid such as p-toluenesulfonic acid in a solventsuch as dimethylisobutylketone:

in which R¹¹, R¹², R¹³, R¹⁴, A¹¹, A¹² and A¹³ are as defined above,R^(11b) represents a C1-C6 divalent saturated hydrocarbon group, andR^(14b) represents a C1-C6 divalent saturated hydrocarbon group. Thereaction can be conducted at temperature of preferably 5° C. to 60° C.,for 0.5 to 24 hours.

Examples of the compound represented by the formula (I-d) include thefollowing compounds which are available on the market.

Examples of the compound represented by the formula (I-e) include thefollowing compounds which are available on the market.

The content of the structural unit (I0) is generally 0.1% to 50% bymole, preferably 1% to 30% by mole, still preferably 2% to 10% by molerelative to all of the structural units in Resin (A).

Resin (A) may have two or more of structural units (I0) different fromeach other.

Preferably Resin (A) may further have a structural unit having anacid-labile group.

Preferably Resin (A) may further have a structural unit having noacid-labile group such as a structural unit (s).

<Structural Unit (a1)>

Preferably, the resin (A) further has a structural unit having anacid-labile group. The structural unit having an acid-labile group issometimes referred to as “structural unit (a1)”.

Herein, the “acid-labile group” means a functional group having aleaving group which is removed therefrom by contacting with an acid togive a hydrophilic group such as a hydroxy group or carboxy group.

The structural unit (a1) is derived from a monomer having an acid-labilegroup which is sometimes referred to as “monomer (a1)”.

Specific examples of the acid-labile group include a group representedby the formula (1):

wherein R^(a1), R^(a2) and R^(a3) each independently represent a C1-C8alkyl group, a C3-C20 alicyclic hydrocarbon group or a combination ofthem, or R^(a1) and R^(a2) may be bonded each other to form a C3-C20divalent alicyclic hydrocarbon group together with the carbon atombonded to both of them, “na” represents an integer of 0 or 1, and *represents a binding site,

and a group represented by the formula (2):

wherein R^(a1′) and R^(a2′) each independently represent a hydrogen atomor a C1-C12 hydrocarbon group, and R^(a3′) represents a C1-C20hydrocarbon group, or R^(a3′) is bonded to R^(a1′) or R^(a2′) to form aC2-C20 divalent heterocyclic group with a carbon atom and X bondedthereto, a methylene group in the divalent heterocyclic group may bereplaced by —O— or —S—, X represents an oxygen atom or a sulfur atom,and * represents a binding site.

Specific examples of the C1-C8 alkyl group include a methyl group, anethyl group, a propyl group, an isopropyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group and an octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.

Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, adimethylcyclohexyl group, a cycloheptyl group and a cyclooctyl group)and a polycyclic alicyclic hydrocarbon group such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group, and the followings.

The alicyclic hydrocarbon group preferably has C3-C16 carbon atoms. Thecombination of alkyl group and alicyclic hydrocarbon group includes amethylcyclohexyl group, a dimethylcyclohexyl group, a methylnorbornylgroup, a cyclohexylmethyl group, an adamantylmethyl group, anorbornylethyl group.

When R^(a1) and R^(a2) of formula (1) are bonded each other to form aC2-C20 divalent hydrocarbon group, examples of the moiety represented by—C(R^(a1))(R^(a2))(R^(a3)) include the following groups and the ringpreferably has 3 to 12 carbon atoms:

wherein R^(a3) is as defined above and * represents a binding site to—O— of formula (1).

As the group represented by the formula (1), preferred are1,1′-dialkylalkoxylcarbonyl group, i.e., the group represented by theformula (1) wherein R^(a1), R^(a2) and R^(a3) each independentlyrepresent a C1-C8 alkyl group, preferably a tert-butyl group;

2-alkyladaman-2-tyloxycarbonyl group, i.e., the group represented by theformula (1) wherein R^(a1) and R^(a2) are bonded each other to form anadamantyl group and R^(a3) is a C1-C8 alkyl group; and a1-(1-adaman-1-tyl)-1-alkylalkoxycarbonyl group, i.e., the grouprepresented by the formula (1) wherein R^(a1) and R^(a2) are C1-C8 alkylgroups and R^(a3) is an adamantyl group.

As to formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the alkyl group and the alicyclic hydrocarbon group includethe same as described above. Examples of the aromatic hydrocarbon groupinclude an aryl group such as a phenyl group, a naphthyl group, ananthryl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, a phenanthryl group, a2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the divalent heterocyclic group formed by bonding withR^(a2) or R^(a1′) with a carbon atom and X bonded thereto include thefollowing groups.

In each formula, R^(a1′) and X are as defined above. Preferably, atleast one of R^(a1′) and R^(a2′) is a hydrogen atom.

Examples of the group represented by formula (2) include the following.

The monomer (a1) is preferably a compound having an acid-labile groupand a carbon-carbon double bond, and is more preferably a (meth)acrylatecompound having an acid-labile group.

Such (meth)acrylate compound preferably has a C5-C20 alicyclichydrocarbon group. When the photoresist composition has a resin whichhas a structural unit with a bulky structure such as a saturatedalicyclic hydrocarbon group, the photoresist composition can provide aphotoresist pattern with excellent resolution.

Specific examples of the structural unit derived from the (meth)acrylatecompound having a group of formula (1) include those represented by theformulae (a1-0), (a1-1) and (a1-2). The structural units represented bythe formulae (a1-0), (a1-1) and (a1-2) are sometimes referred to as“structural unit (a1-0)”, “structural unit (a1-1)” and “structural unit(a1-2)”, respectively. The monomers from which the structural unit(a1-0), (a1-1) and (a1-2) are derived are sometimes referred to as“monomer (a1-0)”, “monomer (a1-1)” and “monomer (a1-2)”, respectively.

In formulae (a1-0), (a1-1) and (a1-2), L^(a01) each independentlyrepresents an oxygen atom or *—O— (CH₂)_(k01)—CO—O— in which *represents a binding site to —CO—, and k01 represents an integer of 1 to7; R^(a01) each independently represent a hydrogen atom or a methylgroup; R^(a02), R^(a03) and R^(a04) each independently represent a C1-C8alkyl group, a C3-C18 alicyclic hydrocarbon group, or a combination ofthem. L^(a1) and L^(a2) each independently represents an oxygen atom or*—O—(CH₂)_(k1)—CO—O— in which * represents a binding site to —CO—, andk1 represents an integer of 1 to 7;

R^(a6) and R^(a5) each independently represent a hydrogen atom or amethyl group;

R^(a6) and R^(a7) each independently represent a C1-C8 alkyl group, aC3-C18 alicyclic hydrocarbon group, or a combination of them;

“m1” represents an integer of 0 to 14; “n1” represents an integer of 0to 10; and “n1′” represents 0 to 3.

L^(a01) is preferably an oxygen atom or *—O— (CH₂)_(f01)—CO—O— inwhich * represents a binding site to —CO—, and “f01” represents aninteger of 1 to 4, and is more preferably an oxygen atom.

“f01” represents preferably an integer of 1 to 4, more preferably 1.

Examples of the alkyl group, the alicyclic hydrocarbon group and thecombination of them, represented by R^(a02), R^(a03) and R^(a04),include those same as examples of the alkyl group, the alicyclichydrocarbon group and the combination of them for R^(a1), R^(a2) andR^(a1) The alkyl group represented by R^(a02), R^(a03) or R^(a04) ispreferably a C1-C6 alkyl group.

The alicyclic hydrocarbon group represented by R^(a02), R^(a03) orR^(a04) has preferably 8 or less, and more preferably 6 or less ofcarbon atoms.

The combination of the alkyl group and the alicyclic hydrocarbon group,as a group represented by R^(a02), R^(a03) or R^(a04), has preferably 18or less of carbon atoms. Examples of the combination include amethylcyclohexyl group, dimethylcyclohexyl group, a methylnorbornylgroup, a methyladamantyl group, a (cyclohexyl)methyl group, a methylcyclohexylmethyl group, an adamantylmethyl group, and a norbornylmethylgroup.

R^(a02) and R^(a03) are each preferably a C1-C6 alkyl group, morepreferably a methyl group or an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group or a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group or an adamantyl group.

L^(a1) and L^(a2) are preferably an oxygen atom or *—O— (CH₂)_(f1)—CO—O—in which * represents a binding site to —CO—, and “f1” represents aninteger of 1 to 4, and is more preferably an oxygen atom.

“f1” represents preferably an integer of 1 to 4, more preferably aninteger of 1.

R^(a4) and R^(a5) are each preferably a methyl group.

Examples of the alkyl group, the alicyclic hydrocarbon group and thecombination of them, represented by R^(a6) and R^(a7), include thosesame as examples for R^(a1), R^(a2) and R^(a3).

The alkyl group represented by R^(a6) or R^(a7) is preferably a C1-C6alkyl group.

The alicyclic hydrocarbon group represented by R^(a6) or R^(a7) haspreferably 8 or less, more preferably 6 or less of carbon atoms.

“m1” is preferably an integer of 0 to 3, and more preferably 0 or 1.“n1” is preferably an integer of 0 to 3, and more preferably 0 or 1.“n1′” is preferably 0 or 1.

The structural unit (a1-0) is preferably one represented by any one ofthe following formulae, and more preferably one represented by any oneof formulae (a1-0-1) to (a1-0-10).

Other examples of the structural unit (a1-0) include those representedby the above-mentioned formulae in which a methyl group bonded to itsmain chain has been replaced by a hydrogen atom.

Examples of the structural unit (a1-1) include those derived from amonomer (a1-1) as recited in JP2010-204646A1. Preferred are thestructural units represented by of formulae (a1-1-1) to (a1-1-8).

As the structural unit (a1-2), preferred are those represented byformulae (a1-2-1) to (a1-2-12), more preferred are those represented byformulae (a1-2-3), (a1-2-4), (a1-2-9) and (a1-2-10), more preferred arethose represented by formulae (a1-2-3) and (a1-2-9).

When the resin (A) has at least one of the structural units (a1-0),(a1-1) and (a1-2), the content of the structural unit in the resin isusually 10 to 95% by mole, preferably 15 to 90% by mole, and morepreferably 20 to 85% by mole based on all the structural units of theresin (A).

Another example of the structural unit (a1) includes a structural unitrepresented by the formula (a1-5).

In the formula (a1-5), R^(a8) represents a hydrogen atom, a halogen atomor a C1-C6 alkyl group that may have a halogen atom,

-   -   Z^(a1) represent a single bond or *—(CH₂)_(h3)—CO-L⁵⁴-, where h3        represents an integer of 1 to 4, * represents a binding site to        L⁵¹, and L⁵⁴ represents —O— or —S—,    -   L⁵¹, L⁵² and L⁵³ each independently represent —O— or —S—,    -   “s1” represents an integer of 1 to 3, and    -   “s1′” represents an integer of 0 to 3.

The structural unit represented by the formula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

R^(a8) is preferably a hydrogen atom, a methyl group or atrifluoromethyl group.

L⁵¹ is preferably —O—.

L⁵² and L⁵³ are independently preferably —O— or —S—, and more preferablyone is —O— and the other is —S—.

“s1” is preferably 1.

“s1′” is preferably an integer of 0 to 2.

Z^(a1) is preferably a single bond or *—CH₂—CO—O— where * represents abinding site to L⁵¹.

Examples of the monomer from which the structural unit (a1-5) is derivedinclude the monomers described in JP2010-61117A1. Among these, themonomers are preferably the following monomers represented by formula(a1-5-1) to formula (a1-5-4), and more preferably monomers representedby formula (a1-5-1) and formula (a1-5-2).

When the resin (A) has a structural unit (a1-5), the content of thestructural unit is usually 1 to 50% by mole, preferably 3 to 45% by moleand more preferably 5 to 40% by mole based on all the structural unitsof the resin.

Examples of the structural unit (a1) further include the followingstructural units.

Examples of the structural unit (a1) having the group represented byformula (2) include a structural unit represented by formula (a1-4). Thestructural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^(a32) represents a hydrogen atom, a halogen atom or aC1-C6 alkyl group that may have a halogen atom,

R^(a33) in each occurrence independently represent a halogen atom, ahydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acylgroup, a C2-C4 acyloxy group, an acryloyloxy group or methacryloyloxygroup,

“la” represents an integer 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group; and

R^(a36) represents a C1-C20 hydrocarbon group, or R^(a35) and R^(a36)may be bonded together with a C—O bonded thereto to form a divalentC3-C20 heterocyclic group, and a methylene group contained in thehydrocarbon group or the divalent heterocyclic group may be replaced byan oxygen atom or a sulfur atom.

Examples of the alkyl group of R^(a32) and R^(a33) include methyl,ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkylgroup is preferably a C1-C4 alkyl group, and more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom of R^(a32) and R^(a33) include a fluorine,chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom includetrifluoromethyl, difluoromethyl, methyl, perfluoroethyl,1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl,1,1,1,2,2-pentafluoropropyl, propyl, perfluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl,1,1,1,2,2,3,3,4,4-nonafluoropentyl, n-pentyl, n-hexyl andn-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy and hexyloxy groups. The alkoxy group is preferably a C1-C4alkoxy group, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups.

Examples of the hydrocarbon group for R^(a34) and R^(a35) are the sameexamples as described in R^(ale) to R^(a2′) in the formula (2).

Examples of hydrocarbon group for R^(a36) include a C1-C18 alkyl group,a C3-018 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbongroup or a group formed by combining thereof.

In the formula (a1-4), R^(a32) is preferably a hydrogen atom. R^(a33) ispreferably a C1-C4 alkoxy group, more preferably a methoxy group or anethoxy group, and still more preferably a methoxy group.

“la” is preferably 0 or 1, and more preferably 0.

R^(a34) is preferably a hydrogen atom.

R^(a35) is preferably a C1-C12 hydrocarbon group, and more preferably amethyl group or an ethyl group.

The hydrocarbon group for R^(a36) is preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a combination thereof, and more preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group or a C7-C18 aralkyl group. The alkylgroup and the alicyclic hydrocarbon group for R^(a36) are preferablyunsubstituted. When the aromatic hydrocarbon group of R^(a36) has asubstituent, the substituent is preferably a C6-C10 aryloxy group.

Examples of the structural unit (a1-4) include those derived from themonomers described in JP2010-204646A1. Among them, the structural unitis preferably the following ones represented by formula (a1-4-1) toformula (a1-4-8), and more preferably the structural units representedby formula (a1-4-1) to formula (a1-4-5), and formula (a1-4-8).

When the resin (A) has the structural unit (a1-4), the proportionthereof is preferably 10% by mole to 95% by mole, more preferably 15% bymole to 90% by mole, and still more preferably 20% by mole to 85% bymole, based on the all the structural units of the resin (A) (100% bymole).

The resin (A) has, as the structural unit (a1), preferably at least one,more preferably two or more structural units selected from thestructural unit (a1-0), the structural unit (a1-1), the structural unit(a1-2), still more preferably a combination of the structural unit(a1-1) and the structural unit (a1-2), a combination of the structuralunit (a1-1), a combination of the structural unit (a1-1) and thestructural unit (a1-0), a combination of the structural unit (a1-2) andthe structural unit (a1-0), a combination of the structural unit (a1-0),the structural unit (a1-1) and the structural unit (a1-2), and furtherstill preferably a combination of the structural unit (a1-1) and thestructural unit (a1-2).

The resin (A) may further have a structural unit having no acid-labilegroup.

The structural unit having no acid-labile group preferably has a hydroxygroup or lactone group. Such a structural unit having a hydroxy group orlactone group is sometimes referred to as “structural unit (s)”. Thestructural unit having not acid-labile group but a hydroxy group issometimes referred to as “structural unit (a2)”. The structural unithaving not acid-labile group but a lactone group is sometimes referredto as “structural unit (a3)”. The resin (A) which has a structural unit(s) can give a photoresist composition capable of providing aphotoresist pattern with improved resolution and adhesiveness to asubstrate.

The structural unit (a2) may have an alcoholic hydroxy group or aphenolic-hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, preferred is a resin which has a structural unit(a2) having a phenolic-hydroxy group.

When ArF excimer laser (wavelength: 193 nm) is used as an exposuresystem, preferred is a resin which has the structural unit (a2) havingan alcoholic hydroxy group.

Examples of the structural unit (a2) having a phenolic-hydroxy groupinclude one derived from a hydroxystyrene.

When the resin (A) further has the structural unit (a2) having aphenolic-hydroxy group, the proportion thereof is preferably 5 to 95% bymole, more preferably 10 to 80% by mole, and still more preferably 15 to80% by mole, based on all the structural units of the resin (A).

Preferred examples of the structural unit (a2) having an alcoholichydroxy group include a structural unit represented by the formula(a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents an oxygen atom or *—O—(CH₂)_(k2)—CO—O— in which * represents a binding site to —CO—, and k2represents an integer of 1 to 7, and o1 represents an integer of 0 to10. In the formula (a2-1), L^(a3) is preferably an oxygen atom or*—O—(CH₂)_(f2)—CO—O— in which * represents a binding site to —CO—, andf2 represents an integer of 1 to 4, is more preferably an oxygen atomand *—O—CH₂—CO—O—, and is still more preferably an oxygen atom.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably 0, 1, 2 or 3 and is more preferably 0 or 1.

Examples of the monomer from which the structural unit represented bythe formula (a2-1) is derived include those mentioned inJP2010-204646A1. Examples of the structural unit represented by theformula (a2-1) preferably include those represented by formulae(a2-1-1), (a2-1-2), (a2-1-3), (a2-1-4), (a2-1-5) and (a2-1-6), and morepreferably those represented by formulae (a2-1-1), (a2-1-2), (a2-1-3)and (a2-1-4), still more preferably those represented by formulae(a2-1-1) and (a2-1-3).

When the resin (A) further has the structural unit represented by theformula (a2-1), the content of the structural unit represented by theformula (a2-1) is usually 1 to 45% by mole and preferably 1 to 40% bymole, more preferably 1 to 35% by mole, still more preferably 2 to 20%by mole, still further more preferably 2 to 5% by mole, based on all thestructural units of the resin (A).

In the structural unit (a3), examples of the lactone ring include amonocyclic lactone ring such as β-propiolactone ring, γ-butyrolactonering and δ-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring.

Among them, preferred are γ-butyrolactone ring and a condensed lactonering formed from γ-butyrolactone ring and another ring. Preferableexamples of the structural unit (a3) include those represented by theformulae (a3-1), (a3-2), (a3-3) and (a3-4):

wherein L^(a4), L^(a5) and L^(a6) each independently represent —O— or*—O—(CH₂)_(k3)—CO—O— in which * represents a binding site to —CO— and k3represents an integer of 1 to 7,

L^(a7) represents a single bond, *-L^(a8)-O—, *-L^(a8)-CO—O—,

*-L^(a8)-CO—O-L^(a9)-CO—O—, or *-L^(a8)-O—CO-L^(a9)-O—; * represents abinding site to a carbonyl group, L^(a8) and L^(a9) each represent aC1-C6 alkanediyl group,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a21) represents a C1-C4 aliphatic hydrocarbon group, R^(a22), R^(a23)and

R^(a25) are independently in each occurrence a carboxyl group, a cyanogroup or a C1-C4 aliphatic hydrocarbon group, R^(a24) represents ahydrogen atom, a halogen atom or a C1-C6 alkyl group optionally having ahalogen atom, p1 represents an integer of 0 to 5, q1 and r1 eachindependently represent an integer of 0 to 3, and w1 represents aninteger of 0 to 8.

Examples of the aliphatic hydrocarbon group for R^(a21), R^(a22),R^(a23) and R^(a25) include an alkyl group such as methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl groups.

Examples of the alkanediyl group of L^(a8) and L^(a9) include methylene,ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl,pentane-1,5-diyl, hexane-1,6-diyl, butane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4-diyl and2-methylbutane-1,4-diyl groups.

L^(a4), La⁵ and L^(a6) each independently represent preferably —O— or*—O—(CH₂)_(d1)—CO—O— in which * represents a binding site to —CO— and d1represents an integer of 1 to 4, and more preferably —O— and*—O—CH₂—CO—O—, and still more preferably —O—.

Preferably, R^(a18), R^(a19) and R^(a20) are independently in eachoccurrence a methyl group.

Preferably, R^(a22) and R^(a23) are independently in each occurrence acarboxyl group, a cyano group or a methyl group.

p1, q1, r1 and w are independently in each occurrence preferably aninteger of 0 to 2, and more preferably 0 or 1.

Examples of the halogen atom for R^(a24) include fluorine, chlorine,bromine and iodine atoms.

Examples of the alkyl group for R^(a24) include methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl groups.The alkyl group is preferably a C1-C4 alkyl group, more preferably amethyl group or an ethyl group.

Examples of the alkyl group having a halogen atom for R^(a24) includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl, perfluorohexyl, trichloromethyl, tribromomethyl andtriiodomethyl groups.

R^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably a single bond or *-L^(a8)-CO—O—, and morepreferably a single bond, *—CH₂—CO—O— or *—C₂H₄—CO—O—.

The structural unit represented by formula (a3-4) is preferably onerepresented by formula (a3-4)′.

In formula (a3-4)′, R^(a24) and L^(a7) are as defined above.

Examples of the monomers from which the structural unit (a3) is derivedinclude those mentioned in JP2010-204646A1, JP2010-122294A1, andJP2010-41274A1. Examples of the structural unit (a3) include preferablythose represented by the formulae (a3-1-1) to (a3-1-4), the formulae(a3-2-1) to (a3-2-4), the formulae (a3-3-1) to (a3-3-4), and theformulae (a3-4-1) to (a3-4-12), more preferably those represented by theformulae (a3-1-1), (a3-1-2), (a3-2-1), (a3-2-3), (a3-2-4), (a3-4-1) to(a3-4-12), still more preferably those represented by the formulae(a3-4-1) to (a3-4-12), and furthermore preferably those represented bythe formulae (a3-4-1) to (a3-4-6).

Examples of the structural unit (a3) further include those representedby formulae (a3-4-1) to (a3-4-12) in which a methyl group has beenreplaced by a hydrogen atom.

When the resin (A) has the structural unit (a3), the total content ofthe structural unit (a3) is usually 5 to 70% by mole, preferably 10 to65% by mole, and more preferably 10 to 60% by mole, based on all thestructural units of the resin (A).

When the resin (A) has the structural unit (a3-1), (a3-2), (a3-3) or(a3-4), each content of them is usually 5 to 60% by mole, preferably 5to 50% by mole, and more preferably 10 to 50% by mole, based on all thestructural units of the resin (A).

The resin (A) may further have a structural unit other than thestructural units (a1), (a2) and (a3). The structural unit other than thestructural units (a1), (a2) and (a3) is sometimes referred to as the“structural unit (t)”.

Examples of the structural unit (t) include a structural unit having ahalogen atom such as a fluorine atom and a structural unit which has ahydrocarbon group having no acid-labile group.

As to the structural unit (t), examples of the structural unit having ahalogen atom, which structural unit is sometimes referred to as“structural unit (a4)”, include a structural unit represented by formula(a4-0).

In the formula (a4-0), R⁵ represents a hydrogen atom or a methyl group,L⁵ represents a single bond or a C1-C4 saturated aliphatic hydrocarbongroup, L³ represents a C1-C8 perfluoroalkanediyl group, or a C3-C12perfluorocycloalkanediyl group, and R⁶ represents a hydrogen atom or afluorine atom.

Examples of the saturated aliphatic hydrocarbon group for L⁵ includeC1-C4 alkanediyl group, i.e., a linear alkanediyl group such asmethylene, ethylene, propane-1,3-diyl, and butane-1,4-diyl groups; and abranched alkanediyl group such as ethane-1,1-diyl, propane-1,2-diyl,butane-1,3-diyl, 2-methylpropane-1,3-diyl and 2-methylpropane-1,2-diylgroups.

L⁵ is preferably a single bond, methylene or ethylene group, and morepreferably a single bond or methylene group.

Examples of the perfluoroalkanediyl group for L³ includedifluoromethylene, perfluoroethylene, perfluoropropane-1,3-diyl,perfluoropropane-1,2-diyl, perfluoropropane-2,2-diyl,perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl,perfluorobutane-1,2-diyl, perfluoropentane-1,5-diyl,perfluoropentane-2,2-diyl, perfluoropentane-3,3-diyl,perfluorohexane-1,6-diyl, perfluorohexane-2,2-diyl,perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl,perfluoroheptane-2,2-diyl, perfluoroheptane-3,4-diyl,perfluoroheptane-4,4-diyl, perfluorooctan-1,8-diyl,perfluorooctan-2,2-diyl, perfluorooctan-3,3-diyl andperfluorooctan-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L³ includeperfluorocyclohexanediyl, perfluorocyclopentanediyl,perfluorocycloheptanediyl and perfluoroadamantanediyl groups.

L³ is preferably a C1-C6 perfluoroalkanediyl group, more preferably aC1-C3 perfluoroalkanediyl group.

Examples of the structural unit represented by formula (a4-0) includethose as follow.

Examples of the structural unit (a4) include those represented byformula (a4-1):

wherein R^(a41) represents a hydrogen atom or a methyl group,

R^(a42) represents an optionally substituted C1-C20 hydrocarbon groupwhere a methylene group may be replaced by an oxygen atom or a carbonylgroup, and

A^(a41) represents an optionally substituted C1-C6 alkanediyl group or agroup represented by formula (a-g1):

wherein s represents 0 or 1,

A^(a42) and A^(a44) each independently represent an optionallysubstituted C1-C5 divalent aliphatic hydrocarbon group,

A^(a43) represents a single bond or an optionally substituted C1-C5divalent aliphatic hydrocarbon group, and

X^(a41) and X^(a42) each independently represent —O—, —CO—, —CO—O— or—O—CO—,

provided that the total number of the carbon atoms contained in thegroup of A^(a42), A^(a43), A^(a44), X^(a41) and X^(a42) is 7 or less, atleast one of A^(a41) and R^(a42) has a halogen atom as a substituent,and

* and ** represent a binding site, and * represents a binding site to—O—CO—R^(a42).

The hydrocarbon group for R^(a42) may be a chain aliphatic hydrocarbongroup, a cyclic aliphatic hydrocarbon group, an aromatic hydrocarbongroup, or a combination thereof.

The chain aliphatic hydrocarbon group and the cyclic aliphatichydrocarbon group may have a carbon-carbon unsaturated bond, and ispreferably a chain and a cyclic saturated aliphatic hydrocarbon group.Examples of the saturated aliphatic hydrocarbon group include a linearor branched alkyl group, a monocyclic or polycyclic alicyclichydrocarbon group, and an aliphatic hydrocarbon group formed bycombining the alkyl group and the alicyclic hydrocarbon group.

Examples of the chain aliphatic hydrocarbon group include an alkyl groupsuch as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,decyl, dodecyl and hexadecyl groups.

Examples of the alicyclic hydrocarbon group include a cycloalkyl groupsuch as cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl groups; andpolycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl andnorbornyl groups as well as groups below. * represents a binding site.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, biphenyl, phenanthryl and fluorenyl groups.

The hydrocarbon group for R^(a42) is preferably a chain aliphatichydrocarbon group, a cyclic aliphatic hydrocarbon group, and acombination thereof. The hydrocarbon group may have a carbon-carbonunsaturated bond, is preferably a chain saturated aliphatic hydrocarbongroup, a cyclic saturated aliphatic hydrocarbon group, and a combinationthereof.

Examples of the substituent for R^(a42) include a halogen atom and agroup represented by formula (a-g3):*-X^(a43)-A^(a45)  (a-g3)

wherein X^(a43) represent an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group,

A^(a45) represents a C1-C17 aliphatic hydrocarbon group that has ahalogen atom, and

* represents a binding site.

Examples of the halogen atom include fluorine, chlorine, bromine oriodine atom, and preferably a fluorine atom.

Examples of the aliphatic hydrocarbon group for A^(a45) include the sameones as those for R^(a42).

R^(a42) is preferably an aliphatic hydrocarbon group that may have ahalogen atom, and more preferably an alkyl group having a halogen atomand/or an aliphatic hydrocarbon group having the group represented bythe formula (a-g3).

When R^(a42) is an aliphatic hydrocarbon group having a halogen atom, analiphatic hydrocarbon group having a fluorine atom is preferred, aperfluoroalkyl group or a perfulorocycloalkyl group are more preferred,a C1-C6 perfluoroalkyl group is still more preferred, a C1-C3perfluoroalkyl group is particularly preferred.

Examples of the perfluoroalkyl group include perfluoromethyl,perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl,perfluorohexyl, perfluoroheptyl and perfluorooctyl groups. Examples ofthe perfluorocycloalkyl group include perfluorocyclohexyl group.

The aliphatic hydrocarbon group having the group represented by theformula (a-g3) is more preferably a group represented by formula (a-g2):*-A^(a46)-X^(a44)-A^(a47)  (a-g2)

wherein A^(a46) represents a C1-C17 aliphatic hydrocarbon group that mayhave a halogen atom,

X^(a44) represent a carbonyloxy group or an oxycarbonyl group,

A^(a47) represents a C1-C17 aliphatic hydrocarbon group that may have ahalogen atom,

provided that the total number of the carbon atoms contained in thegroup of A^(a46), X^(a44) and A^(a47) is 18 or less,

at least one of A^(a46) and A^(a47) has a halogen atom, and

* represents a binding site to a carbonyl group.

The aliphatic hydrocarbon group for A^(a46) has preferably 1 to 6 carbonatoms, more preferably 1 to 3, carbon atoms.

The aliphatic hydrocarbon group for A^(a47) has preferably 4 to 15carbon atoms, more preferably 5 to 12 carbon atoms. A^(a47) is morepreferably a cyclohexyl group or an adamantyl group. Preferred examplesof *-A^(a46)-X^(a44)-A^(a47) include the following ones.

Examples of the alkanediyl group for A^(a41) include a linear alkanediylgroup such as methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl,pentane-1,5-diyl and hexane-1,6-diyl groups;

a branched alkanediyl group such as propane-1,2-diyl, butan-1,3-diyl,2-methylpropane-1,2-diyl, l-methylbutane-1,4-diyl,2-methylbutane-1,4-diyl groups.

Examples of the substituent on the alkanediyl group for A^(a41) includea hydroxy group and a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably ethylene group.

In the group represented by the formula (a-g1) (which is sometimesreferred to as “group (a-g1)”), examples of the aliphatic hydrocarbongroup for A^(a42), A^(a43) and A^(a44) include methylene, ethylene,propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl,l-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl and2-methylpropane-1,2-diyl groups.

Examples of the substituent on the aliphatic hydrocarbon group forA^(a42), A^(a43) and A^(a44) include a hydroxy group and a C1-C6 alkoxygroup.

s is preferably 0.

Examples of the group (a-g1) in which X^(a42) represents an oxygen atominclude the following ones. In the formulae, * and ** each represent abinding site, and ** represents a binding site to —O—CO—R^(a42).

Examples of the group (a-g1) in which X^(a42) represents a carbonylgroup include the following ones. In the formulae, * and ** are asdefined above.

Examples of the group (a-g1) in which X^(a42) represents a carbonyloxygroup include the following ones. In the formulae, * and ** are asdefined above.

Examples of the group (a-g1) in which X^(a42) represents an oxycarbonylgroup include the following ones. In the formulae, * and ** are asdefined above.

The structural unit represented by the formula (a4-1) is preferably astructural unit represented by formula (a4-2):

wherein R^(f1) represents a hydrogen atom or a methyl group,

A^(f1) represent a C1-C6 alkanediyl group, and

R^(f2) represents a C1-C10 hydrocarbon group that has a fluorine atom.Examples of the alkanediyl group for A^(f1) include a linear alkanediylgroup such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl,butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diyl groups; a branchedalkanediyl group such as l-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,l-methylbutane-1,4-diyl and 2-methylbutane-1,4-diyl groups.

Examples of the hydrocarbon group for R^(f2) include an aliphatichydrocarbon group and an aromatic hydrocarbon group. The aliphatichydrocarbon group includes chain and cyclic groups, and a combinationthereof. The aliphatic hydrocarbon group is preferably an alkyl groupand a cyclic aliphatic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and2-ethylhexyl groups.

Examples of the cyclic aliphatic hydrocarbon group include any of amonocyclic group and a polycyclic group. Examples of the monocyclicalicyclic hydrocarbon group include a cycloalkyl group such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups.Examples of the polycyclic hydrocarbon groups includesdecahydronaphthyl, adamantyl, 2-alkyladamantane-2-yl,1-(adamantane-1-yl)alkane-1-yl, norbornyl, methylnorbornyl and isobornylgroups.

Examples of the hydrocarbon group having a fluorine atom for R^(f2)include an alkyl group having a fluorine atom and an alicyclichydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include afluorinated alkyl group such as difluoromethyl, trifluoromethyl,1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl,perfluoropropyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodeca fluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

In the formula (a4-2), A^(f1) is preferably a C2-C4 alkanediyl group,and more preferably an ethylene group.

R^(f2) is preferably a C1-C6 fluorinated alkyl group.

Examples of the alkanediyl group for A^(f11) include the same ones asthose for A^(f1).

Examples of the structural unit represented by formula (a4-2) includestructural units represented by formula (a4-1-1) to formula (a4-1-22).

Examples of the structural unit (a4) further include the following ones.

When Resin (A) has the structural unit (a4), the content thereof isusually 1 to 20% by mole, preferably 2 to 15% by mole, and morepreferably 3 to 10% by mole, based on all the structural units of theresin (A).

The structural unit which has a hydrocarbon group having no acid-labilegroup, which is sometimes referred to as the “structural unit (a5)”, mayhave a linear, branched or cyclic hydrocarbon group, preferably analicyclic hydrocarbon group.

Examples of the structural unit (a5) include one represented by formula(a5-1):

where R⁵¹ represents a hydrogen atom or a methyl group;

R⁵² represents a C3-C18 alicyclic hydrocarbon group, provided that thealicyclic hydrocarbon group has no substituent on the carbon atom bondedto L⁵⁵; and

L⁵⁵ represents a single bond or a C1-C8 alkanediyl group where amethylene group can be replaced by an oxygen atom or carbonyl group. Thealicyclic hydrocarbon group represented by R⁵² may be monocyclic orpolycyclic one. Examples of the alicyclic hydrocarbon group include amonocyclic hydrocarbon group such as a C3-C18 cycloalkyl group (e.g. acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup) and a polycyclic alicyclic hydrocarbon group such as an adamantylgroup, or a norbornyl group.

Examples of the alicyclic hydrocarbon group having a substituent includea 3-hydroxyadamantyl group, and a 3-methyladamantyl group. Examples ofthe C1-C8 aliphatic hydrocarbon group include an alkyl group such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,n-pentyl, n-hexyl, n-heptyl, 2-ethylhexyl and n-octyl groups.

Examples of the alicyclic hydrocarbon group having a substituent for R⁵²include 3-methyladamantyl group.

R⁵² is preferably an unsubstituted C3-C18 alicyclic hydrocarbon group,and more preferably an adamantyl, norbornyl or cyclohexyl group.

Examples of the divalent saturated hydrocarbon group for L⁵⁵ include adivalent saturated aliphatic hydrocarbon group and a divalent saturatedalicyclic hydrocarbon group, and a divalent saturated aliphatichydrocarbon group is preferred.

Examples of the divalent saturated aliphatic hydrocarbon group includean alkanediyl group such as methylene, ethylene, propanediyl, butanediyland pentanediyl groups.

Examples of the divalent saturated alicyclic hydrocarbon group includeany of a monocyclic group and a polycyclic group. Examples of themonocyclic group include cycloalkanediyl group such as cyclopentanediyland cyclohexanediyl groups. Examples of the polycyclic group includeadamantanediyl and norbornanediyl groups. Examples of the saturatedhydrocarbon group in which a methylene group has been replaced by anoxygen atom or a carbonyl group include groups represented by formula(L1-1) to formula (L1-4). In formula (L1-1) to formula (L1-4), *represents a binding site to an oxygen atom.

In the formulae, X^(X1) represents an oxycarbonyl group or a carbonyloxygroup,

L^(X1) represents a C1-C16 divalent saturated aliphatic hydrocarbongroup,

L^(X2) represents a single bond or a C1-C15 divalent saturated aliphatichydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X1) and L^(X2) is 16 or less;

L^(X3) represents a single bond or a C1-C17 divalent saturated aliphatichydrocarbon group,

L^(X4) represents a single bond or a C1-C16 divalent saturated aliphatichydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X3) and L^(X4) is 17 or less;

L^(X5) represents a C1-C15 divalent saturated aliphatic hydrocarbongroup,

L^(X6) and L^(X7) each independently represent a single bond or a C1-C14divalent saturated aliphatic hydrocarbon group,

provided that the total number of the carbon atoms contained in thegroups of L^(X5), L^(X6) and L^(X7) is 15 or less;

L^(X8) and L^(X9) each independently represent a single bond or a C1-C12divalent saturated aliphatic hydrocarbon group,

W^(X1) represents a C3-C15 divalent saturated alicyclic hydrocarbongroup,

provided that the total number of the carbon atoms contained in thegroups of L^(X8), L^(X9) and W^(X1) is 15 or less.

L^(X1) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup, and more preferably a methylene group or an ethylene group.

L^(X2) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond.

L^(X3) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup.

L^(X4) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group.

L^(X5) is preferably a C1-C8 divalent saturated aliphatic hydrocarbongroup, and more preferably a methylene group or an ethylene group.

L^(X6) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a methylene group or anethylene group.

L^(X7) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group.

L^(X8) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond or amethylene group.

L^(X9) is preferably a single bond or a C1-C8 divalent saturatedaliphatic hydrocarbon group, and more preferably a single bond or amethylene group.

W^(X1) is preferably a C3-C10 divalent saturated alicyclic hydrocarbongroup, and more preferably a cyclohexanediyl group and an adamantanediylgroup.

Examples of the group represented by the formula (L1-1) include thefollowing ones.

Examples of the group represented by the formula (L1-2) include thefollowing ones.

Examples of the group represented by the formula (L1-3) include thefollowing ones.

Examples of the group represented by the formula (L1-4) include thefollowing ones.

L⁵⁵ is preferably a single bond, a methylene group, an ethylene group orthe group represented by the formula (L1-1), more preferably a singlebond or the group represented by the formula (L1-1). Examples of thestructural unit represented by formula (a5-1) include the followingones.

Examples of the structural units represented by formula (a5-1) includestructural units represented by the formulae (a5-1-1) to (a5-1-18) inwhich a methyl group corresponding to R⁵¹ has been replaced by ahydrogen atom.

When the resin (A) further has the structural unit represented byformula (a5), the content thereof is preferably 1 to 30% by mole, morepreferably 2 to 20% by mole, and still more preferably 3 to 15% by mole,based on all the structural units of the resin.

The resin (A) can further have any other structural unit known in thephotoresist field.

The resin (A) is preferably a resin which comprises the structural unit(I0) and the structural unit (a1), more preferably a resin whichcomprises the structural unit (I0), the structural unit (a1) and thestructural unit (a3).

The resin (A) can be produced by polymerizing the compound (I), andother monomers as mentioned above in a manner of radical polymerizationor a known polymerization method. In the polymerization, the compound(I) can act as a chain transfer agent as well as a monomer. For thepolymerization, the compound (I) is used in an amount of usually 0.1% to50% by mole, preferably 1% to 30% by mole, more preferably 2% to 10% bymole, of all monomers to be used therefor.

The weight-average molecular weight of the resin (A) is usually 2,000 ormore, preferably 2,500 or more, and more preferably 3,000 or more, andusually 50,000 or less, preferably 30,000 or less, more preferably15,000 or less.

The weight-average molecular weight can be measured with gel permeationchromatography (standard: polyethylene). The detailed method ofmeasurement is described in Examples of the present specification.

<Photoresist Composition>

The photoresist composition of the disclosure has the resin (A) and anacid generator.

Preferably, the photoresist composition further contains another resinthan the resin (A).

The photoresist composition may further contain a quencher, or asolvent.

The another resin than the resin (A) is any resin which has nostructural unit (I), which is sometimes referred to as “resin (Aa)”.

Examples of structural units for the resin (Aa) include the structuralunits (a1), (a2), (a3) and (a5).

Examples of the resin (Aa) include a resin which consists of astructural unit (a1) and a structural unit (a2) or (a3), a resin whichconsists of a structural unit (a1), a structural unit (a2) or (a3), anda structural unit (t). Preferably, the photoresist composition furthercontains the resin (Aa) which has a structural unit (a1).

The resin (Aa) may have a structural unit (a2), (a3) or (a5) or anotherknown structural unit having no acid-labile group in addition tostructural units (a1).

In the resin (Aa), the content of the structural unit (a1) is preferably10% by mole or more, more preferably 20% by mole or more, and preferably95% by mole or less, more preferably 80% by mole or less based on allthe structural units of the resin.

The resin (Aa) can be produced according to known polymerization methodssuch as radical polymerization, using monomers corresponding to thestructural units as mentioned above.

The resin (Aa) has usually 6000 or more of the weight-average molecularweight, preferably 7000 or more of the weight-average molecular weight,still more preferably 8000 or more of the weight-average molecularweight.

The resin (Aa) usually has 50,000 or less of the weight-averagemolecular weight, preferably has 20,000 or less of the weight-averagemolecular weight.

Examples of another resin than the resin (A) further include any resinwhich has no structural unit (a1), which is sometimes referred to as“resin (X)”.

Examples of structural units for the resin (X) include the structuralunits (t), (a2) and (a3). The resin (X) preferably has a structural unit(a4).

In the resin (X), the content of the structural unit (a4) is preferably40% by mole or more, more preferably 45% by mole or more, still morepreferably 50% by mole or more, based on all the structural units of theresin.

The resin (X) can be produced according to known polymerization methodssuch as radical polymerization, using monomers corresponding to thestructural units as mentioned above.

The resin (X) has usually 6000 or more of the weight-average molecularweight, preferably 7000 or more of the weight-average molecular weight,still more preferably 8000 or more of the weight-average molecularweight.

The resin (X) usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography.

When the photoresist composition contains the resin (X), the resin (A)has preferably the structural unit (a1) therein. When the photoresistcomposition contains the resin (X), the content of the resin ispreferably 0.5 to 60 weight parts, more preferably 1 to 50 weight parts,and still more preferably 1 to 40 weight parts, further more preferably1 to 30 weight parts, and further still more preferably 1 to 10 weightparts, relative to 100 parts of Resin (A).

The total content of all of the resins in the photoresist composition isusually 80% by mass or more, preferably 90% by mass or more based on sumof the solid components, and usually 99% by mass or less. In thisspecification, “solid component” means components other than solvent inthe photoresist composition. The amount can be measured with a knownanalysis equipment such as gas or liquid chromatography.

The photoresist composition contains an acid generator. There is nolimitation of the acid generator for the photoresist composition,examples of which include those known in the art.

The acid generator is a compound which can be decomposed by light orradiation to generate an acid. The acid generators may be either ionicor non-ionic one. The acid generator can be used singly or incombination of two or more of them.

The non-ionic acid generator includes organic halide, sulfonate esters(e.g., 2-nitrobenzylester, aromatic sulfonate, oxime sulfonate,N-sulfonyloxyimide, sulfonyl oxyketone, diazonaphthoquinone 4-sulfonate)and sulfone (e.g., disulfone, ketosulfone, sulfonyldiazomethane). Theionic acid generator includes an onium salt comprising an onium cation(e.g., a diazonium salt, a phosphonium salt, a sulfonium salt, aniodonium salt). Anions of the onium salts include a sulfonic acid anion,a sulfonylimide anion and a sulfonylmethide anion.

The acid generator includes compounds which generate an acid uponradiation, which are described in JP63-26653A1, JP55-164824A1,JP62-69263A1, JP63-146038A1, JP63-163452A1, JP62-153853A1,JP63-146029A1, U.S. Pat. Nos. 3,779,778, 3,849,137, German patent No.3914407 and European patent No. 126712.

The acid generator is preferably a fluorine-containing acid generator,more preferably a salt represented by formula (B1):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group,

L^(b1) represents a C1-C24 divalent saturated hydrocarbon group where amethylene group can be replaced by an oxygen atom or a carbonyl groupand where a hydrogen atom can be replaced by an fluorine atom or ahydroxy group,

Y represents a methyl group where a hydrogen atom can be replaced by asubstituent, or a C3-C18 alicyclic hydrocarbon group where a methylenegroup can be replaced by an oxygen atom, a sulfonyl group or a carbonylgroup and where a hydrogen atom can be replaced by a substituent, and

Z⁺ represents an organic cation.

Examples of the perfluoroalkyl group represented by Q¹ and Q² include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group. It is preferred that Q1 and Q² eachindependently represent a fluorine atom or a trifluoromethyl group, andit is more preferred that Q¹ and Q² are fluorine atoms.

Examples of the divalent saturated hydrocarbon group represented byL^(b1) include linear alkanediyl groups, branched chain alkanediylgroups, a monocyclic divalent alicyclic hydrocarbon group, a polycyclicdivalent alicyclic hydrocarbon group and combinations of them.

Specific examples of them include

linear alkanediyl groups such as a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup;

branched chain alkanediyl groups including a group formed by attaching aside chain to a linear alkanediyl group, such as a butan-1,3-diyl group,a2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, apentane-1,4-diyl group, and a 2-methylbutane-1,4-diyl group;

a monocyclic divalent alicyclic hydrocarbon group such as acyclobutan-1,3-diyl group, cyclopentane-1,3-diyl group, acyclohexane-1,2-diyl group, a 1-methylcyclohexane-1,2-diyl group,cyclohexane-1,4-diyl group, cyclooctane-1,2-diyl group, and acyclooctane-1,5-diyl group; and

a polycyclic divalent alicyclic hydrocarbon group such as anorbornane-2,3-diyl group, norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,2-diyl group, anadamantane-1,5-diyl group and an adamantane-1,6-diyl group.

When L^(b1) represents a divalent saturated hydrocarbon group in which amethylene group has been replaced by an oxygen atom or a carbonyl group,examples of L^(b1) include the moiety represented by any one of formulae(b1-1) to (b1-3) as follow;

wherein L^(b2) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom, and

L^(b3) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom or a hydroxyl group and in which a methylene group can be replacedby an oxygen atom or a carbonyl group, provided that the total number ofthe carbon atoms in L^(b2) and L^(b3) is up to 22;

L^(b4) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom, and L^(b5) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom or a hydroxyl group and in which a methylene group can be replacedby an oxygen atom or a carbonyl group, provided that the total number ofthe carbon atoms in L^(b4) and L^(b5) is up to 22;

L^(b6) represents a C1-C15 divalent saturated hydrocarbon group in whicha hydrogen atom can be replaced by a fluorine atom or a hydroxyl group,and L^(b7) represents a single bond or a C1-C15 divalent saturatedhydrocarbon group in which a hydrogen atom can be replaced by a fluorineatom or a hydroxyl group and in which a methylene group can be replacedby an oxygen atom or a carbonyl group, provided that the total number ofthe carbon atoms in L^(b6) and L^(b7) is up to 23; and * represents abinding site to Y.

In formula (b1-1) to formula (b1-3), when a methylene group has beenreplaced by an oxygen atom or a carbonyl group, the carbon number of thesaturated hydrocarbon group corresponds to the number of the carbon atombefore replacement.

Examples of the divalent saturated hydrocarbon group are the sameexamples as the divalent saturated hydrocarbon group of L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b4) is preferably a C1-C8 divalent saturated hydrocarbon group wherea hydrogen atom may be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b6) is preferably a single bond or a C1-C4 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom.

L^(b7) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom or a hydroxy group, and where a methylene group may be replaced byan oxygen atom or a carbonyl group.

Among these, the group represented by the formula (b1-1) or the formula(b1-3) is preferred.

Examples of the divalent group represented by the formula (b1-1) includethe following groups represented by formula (b1-4) to formula (b1-8):

wherein L^(b8) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom or a hydroxy group;

L^(b9) represents a C1-C20 divalent saturated hydrocarbon group, andL^(b10) represents a single bond or a C1-C19 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b9) and L^(b10) is 20 or less;

L^(b1) represents a C1-C21 divalent saturated hydrocarbon group, andL^(b12) represents a single bond or a C1-C20 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b11) and L^(b12) is 21 or less;

L^(b13) represents a C1-C19 divalent saturated hydrocarbon group,L^(b14) represents a single bond or a C1-C18 divalent saturatedhydrocarbon group, and L^(b15) represents a single bond or a C1-C18divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom or a hydroxy group, provided that the totalnumber of carbon atoms contained in the group of L^(b13), L^(b14) andL^(b15) is 19 or less;

L^(b16) represents a C1-C18 divalent saturated hydrocarbon group,L^(b17) represents a C1-C18 divalent saturated hydrocarbon group, andL^(b18) represents a single bond or a C1-C17 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom or a hydroxy group, provided that the total number of carbon atomscontained in the group of L^(b16), L^(b17) and L^(b18) is 19 or less;and * represents a binding site to Y.

L^(b8) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b9) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1-C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b11) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b16) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b7) is preferably a C1-C6 divalent saturated hydrocarbon group.

L^(b18) is preferably a single bond or a C1-C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C4 divalentsaturated hydrocarbon group.

Examples of the divalent group represented by the formula (b1-3) includethe following groups represented by formula (b1-9) to formula (b1-11):

wherein L^(b19) represents a single bond or a C1-C23 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, and L^(b20) represent a single bond or a C1-C23 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, a hydroxy group or an acyloxy group, and a methylene groupcontained in an acyloxy group may be replaced by an oxygen atom or acarbonyl group, and a hydrogen atom contained in an acyloxy group may bereplaced by a hydroxy group, provided that the total number of carbonatoms contained in the group of L^(b19) and L^(b20) is 23 or less;

L^(b21) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b22) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group, and L^(b23) represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom, a hydroxy group or an acyloxy group, and amethylene group contained in an acyloxy group may be replaced by anoxygen atom or a carbonyl group, and a hydrogen atom contained in anacyloxy group may be replaced by a hydroxy group, provided that thetotal number of carbon atoms contained in the group of L^(b2), L^(b22)and L^(b23) is 21 or less;

L^(b24) represents a single bond or a C1-C20 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b2)5 represents a single bond or a C1-C21 divalent saturatedhydrocarbon group, and L^(b26) represents a single bond or a C1-C20divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom, a hydroxy group or an acyloxy group, and amethylene group contained in an acyloxy group may be replaced by anoxygen atom or a carbonyl group, and a hydrogen atom contained in anacyloxy group may be replaced by a hydroxy group, provided that thetotal number of carbon atoms contained in the group of L^(b24), L^(b25)and L^(b26) is 21 or less;

and * represents a binding site to Y.

In formula (b1-9) to formula (b1-11), when a hydrogen atom has beenreplaced by an acyloxy group, the carbon number of the saturatedhydrocarbon group corresponds to the number of the carbon atom, CO and Oin addition to the carbon number of the saturated hydrocarbon group.

Examples of the acyloxy group include acetyloxy, propionyloxy,butyryloxy, cyclohexyl carbonyloxy and adamantyl carbonyloxy groups.

Examples of the acyloxy group having a substituent include oxoadamantylcarbonyloxy, hydroxyadamantyl carbonyloxy, oxocyclohexyl carbonyloxy andhydroxycyclohexyl carbonyloxy groups.

Examples of the group represented by the formula (b1-4) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-5) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-6) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-7) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-8) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-2) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-9) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-10) include thefollowing ones:

where * represents a binding site to Y.

Examples of the group represented by the formula (b1-11) include thefollowing ones:

where * represents a binding site to Y.

Examples of the alicyclic hydrocarbon group represented by Y includethose represented by formulae (Y1) to (Y11) and (Y36) to (Y38).

Examples of the alicyclic hydrocarbon group represented by Y, in which amethylene group can be replaced by an oxygen atom, a sulfonyl group or acarbonyl group, include those represented by formulae (Y12) to (Y35).

Among them, preferred are those represented by formulae (Y1) to (Y20),(Y30) and (Y31), more preferred are those represented by formulae (Y11),(Y15), (Y16), (Y20), (Y30) and (Y31), and still more preferred are thoserepresented by formulae (Y11), (Y15) and (Y30). When Y is a ringstructure represented by any one of formulae (Y28) to (Y33), the ringhas preferably a fluorine atom on an alkanediyl group between two oxygenatoms. In the alkanediyl group, a carbon atom attached to any one of thetwo oxygen atoms has no fluorine atom.

Examples of the substituents for the methyl group represented by Yinclude a halogen atom, a hydroxy group, an oxo group, a C1-C12 alkylgroup, a C3-C16 alicyclic hydrocarbon group, a C6-C18 aromatichydrocarbon group, a glycidyloxy group, or —(CH₂)_(ja)—O—CO—R_(b1) whereR_(b1) represents a C1-C16 alkyl group, a C3-C16 alicyclic hydrocarbongroup, or a C6-C18 aromatic hydrocarbon group optionally substitutedwith a C1-C4 alkyl group. The “ja” represents an integer of 0 to 4.

Examples of the substituents for the alicyclic hydrocarbon grouprepresented by Y include a halogen atom, a hydroxy group, an oxo group,a C1-C12 alkyl group, a C1-C12 hydroxy-containing alkyl group, a C3-C16alicyclic hydrocarbon group, a C1-C12 alkoxy group, a C6-C18 aromatichydrocarbon group optionally substituted with a C1-C4 alkyl group, aC7-C21 aralkyl group, a C2-C4 acyl group, a glycidyloxy group, or—(CH₂)_(j2)—O—CO—R_(b1) where R_(b1) represents a C1-C16 alkyl group, aC3-C16 alicyclic hydrocarbon group, or a C6-C18 aromatic hydrocarbongroup optionally substituted with a C1-C4 alkyl group. The “j2”represents an integer of 0 to 4.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of an aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an antolyl group, a p-methylphenylgroup, p-tert-butylphenyl group, p-adamantylphenyl group, a tolyl group,a xylyl group, a cumenyl group, a mesityl group, a biphenyl group, aphenanthryl group, a 2,6-diethylphenyl group, 2-methyl-6-ethylphenylgroup.

Examples of an aralkyl group include a benzyl group, a phenethyl group,a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of an acyl group include an acetyl group, a propionyl group anda butyryl group.

Examples of the group represented by Y include the following ones.

When Y is a methyl group and L^(b1) is a C3-C17 aliphatic hydrocarbongroup in which a methylene has been replaced by an oxygen atom or acarbonyl group, the aliphatic hydrocarbon group preferably has an oxygenatom or a carbonyl group which is bonded to the methyl group representedby Y.

Y is preferably a C3-C18 alicyclic hydrocarbon group where a methylenegroup can be replaced by an oxygen atom, a sulfonyl group or a carbonylgroup and where a hydrogen atom can be replaced by a substituent, morepreferably an adamantyl group which can have a substituent such as anoxo group or a hydroxyl group, more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or any one of thefollowing groups.

Examples of the sulfonic acid anion of the salt represented by formula(B1) include an anion represented by formulae (B1-A-1) to (B1-A-55), andmore preferably an anions represented by formula (B1-A-1) to formula(B1-A-4), formula (B1-A-9), formula (B1-A-10), formula (B1-A-24) toformula (B1-A-33), formula (B1-A-36) to formula (B1-A-40) and formula(B1-A-47) to formula (B1-A-55).

In formula (B1-A-1) to formula (B1-A-55), R^(i2) to R^(i7) eachindependently represent a C1-C4 alkyl group, and preferably a methylgroup or an ethyl group, R^(i8) represent a C1-C12 aliphatic hydrocarbongroup, preferably a C1-C4 alkyl group, a C5-C12 alicyclic hydrocarbongroup or a group composed of the alkyl group and the alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group or an adamantyl group. L⁴ represents a single bond or aC1-C4 alkanediyl group. Q¹ and Q² represent the same meaning as definedabove.

Specific examples of the anion for the salt represented by formula (B1)include those mentioned in JP2010-204646A1.

Among these, preferred examples of the sulfonic acid anion for the saltrepresented by the formula (B1) include anions represented by formulae(B1a-1) to (B1a-34).

Preferred examples of the sulfonic acid anion include anions representedby the formulae (B1a-1) to (B1a-3), (B1a-7) to (B1a-16), (B1a-18),(B1a-19) and (B1a-22) to (B1a-34).

Examples of the organic cation represented by Z⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation. As Z⁺, an organic sulfonium cation and anorganic iodonium cation are preferred, and an arylsulfonium cation ismore preferred. Herein, the arylsulfonium includes those having one, twoor three aryl groups.

Preferable examples of the organic cation represented by Z⁺ include theorganic cations represented by the formulae (b2-1) to (b2-4):

wherein R^(b4), R^(b5) and R^(b6) independently represent a C1-C30aliphatic hydrocarbon group in which a hydrogen atom can be replaced bya hydroxy group, a C1-C12 alkoxy group or a C6-C18 alicyclic hydrocarbongroup,

a C3-C36 alicyclic hydrocarbon group in which a hydrogen atom can bereplaced by a halogen atom, a C2-C4 acyl group or a glycidyloxy group,and

a C6-C36 aromatic hydrocarbon group in which a hydrogen atom can bereplaced by a halogen atom, a hydroxy group, or C1-C12 alkoxy group; andR^(b4) and R^(b5), R^(b4) and R^(b6), or R^(b5) and R^(b6) can be bondedeach other to form a ring containing S⁺;

R^(b7) and R^(b8) are independently in each occurrence a hydroxy group,a C1-C12 alkyl group or a C1-C12 alkoxy group;

m2 and n2 independently represents an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group, or R^(b9) andR^(b10) are bonded each other to form a ring together with the adjacent—S⁺—, and one or more —CH₂— in the ring may be replaced by an oxygenatom, sulfur atom or carbonyl group; and

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group, or a C6-C18 aromatichydrocarbon group, and R^(b12) represents a C1-C12 aliphatic hydrocarbongroup where a hydrogen atom can be replaced by a C6-C18 aromatichydrocarbon group, a C3-C18 alicyclic hydrocarbon group, and a C6-C18aromatic hydrocarbon group optionally substituted with a C1-C12 alkoxygroup or a C1-C12 alkylcarbonyloxy group; or R^(b11) and R^(b12) arebonded each other to form a C1-C10 divalent alicyclic hydrocarbon groupwhich forms a 2-oxocycloalkyl group together with the adjacent —CHCO—,and one or more —CH₂— in the group may be replaced by an oxygen atom,sulfur atom or carbonyl group; and

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) independentlyrepresent a hydroxy group, a C1-C12 alkyl group or a C1-C12 alkoxygroup;

L^(b31) represents —S— or —O—; and

o2, p2, s2 and t2 each independently represents an integer of 0 to 5;

q2 and r2 each independently represents an integer of 0 to 4; and u2represents 0 or 1.

Examples of the aliphatic hydrocarbon group represented by eachsubstituent include an alkyl group such as a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group, a hexyl group, an octylgroup, and a 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9) to R^(b12) is preferably a C1-C18 alkyl group,more preferably a C1-C12 alkyl group.

Examples of the alkyl group where a hydrogen atom has been replaced byan alicyclic hydrocarbon group include 1-(adamantane-1-yl) alkane-1-ylgroup.

The alicyclic hydrocarbon group represented by each substituent may bemonocyclic or polycyclic, a hydrogen atom of which can be replaced by analkyl group. When a hydrogen atom of it has been replaced by an alkylgroup, the total number of carbon atoms is 30 or less.

Examples of the monocyclic alicyclic hydrocarbon group include acycloalkyl group such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclodecylgroup.

Examples of the polycyclic alicyclic hydrocarbon group include adecahydronaphtyl group, an adamantyl group, a norbornyl group, and thefollowing ones.

The alicyclic hydrocarbon group represented by R^(b9) to R^(b12) haspreferably 3 to 18, more preferably 4 to 12, carbon atoms. Examples ofthe alicyclic hydrocarbon group where a hydrogen atom has been replacedby an alkyl group include a methylcyclohexyl group, a2-alkyladamantane-2-yl group, a methylnorbornyl group, and an isobornylgroup.

Preferable examples of the aromatic hydrocarbon group includesubstituted or unsubstituted phenyl group such as a phenyl group, atolyl group, a xylyl group, a cumenyl group, a mesityl group, a4-ethylphenyl group, 4-tert-butylphenyl group, 4-cyclohexylphenyl group,a 4-adamantylphenyl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group; a biphenyl group, a naphtyl group, aphenanthryl group.

Preferable examples of the aromatic hydrocarbon group where a hydrogenatom has been replaced by an alkoxy group include 4-methoxyphenyl group.

Preferable examples of the alkyl group where a hydrogen atom has beenreplaced by an aromatic hydrocarbon group, i.e., an aralkyl group,include a benzyl group, a phenethyl group, a phenylpropyl group, atrityl group, a naphthylmethyl group and a naphthylethyl group.

When the aromatic hydrocarbon group has an alkyl group or an alicyclichydrocarbon group as a substituent, the substituent is preferably aC1-C12 alkyl group or a C3-C18 alicyclic hydrocarbon group.

Examples of the alkoxy group include a methoxy group, an ethoxy group,apropoxy group, abutoxy group, apentyloxy group, ahexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Preferable examples of the alkylcarbonyloxy group include amethylcarbonyloxy group, an ethylcarbonyloxy group, n-propylcarbonyloxygroup, an isopropylcarbonyloxy group, n-butylcarbonyloxy group,sec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and 2-ethyl hexylcarbonyloxy group.

The ring containing S⁺ formed by bonding R^(b4) and R^(b5), R^(b4) andR^(b6), or R^(b5) and R^(b6) each other may be a monocyclic ring, apolycyclic ring, an aromatic ring, a non-aromatic ring, a saturated ringor a unsaturated ring. The ring can contain a sulfur atom or oxygen atomin addition to S⁺. The ring preferably has 3 to 18 carbon atoms, andmore preferably has 4 to 13 carbon atoms. Examples of such ring include,3 to 12-membered rings, preferably 3 to 7-membered rings, specificallythe following ones.

Examples of the ring group formed by bonding R^(b9) and R^(b10) togetherwith the adjacent S⁺ and the divalent alicyclic hydrocarbon groupinclude, 3 to 12-membered rings, preferably 3 to 7-membered rings,specifically a thiolan-1-ium ring (tetrahydrothiophenium ring), athian-1-ium ring and a 1,4-oxathian-4-ium ring.

Examples of the ring group formed by bonding R^(b11) and R^(b12) include3 to 12-membered rings, preferably 3 to 7-membered rings, specificallyoxocyclopentane ring, oxocyclohexane ring, oxonorbornane ring andoxoadamantane ring.

Among the above-mentioned cations, preferred is the cation representedby the formula (b2-1).

Examples of the cation represented by the formula (b2-1) include thefollowing ones.

Examples of the cation represented by the formula (b2-2) include thefollowing ones.

Examples of the cation represented by the formula (b2-3) include thefollowing ones.

Examples of the cation represented by the formula (b2-4) include thefollowing ones.

The acid generator for the photoresist composition of the disclosure ispreferably those having an anion represented by any one of the formulae(B1a-1) to (B1a-3) and (B1a-7) to (B1a-16) and a cation represented byany one of the formulae (b2-1) and (b2-3).

The acid generator is preferably those represented by formulae (B1-1) to(B1-48), more preferably those having an arylsulfonium cation, stillmore preferably those represented by formulae (B1-1), (B1-3), (B1-5),(B1-7), (B1-11), (B1-14), (B1-20), (B1-26), (B1-29), (B1-31) to (B1-48).

The amount of the acid generator is preferably 1 weight parts or more,more preferably 3 weight parts or more, and preferably 30 weight partsor less, and more preferably 25 weight parts or less, relative to 100weight parts of the resin (A).

The photoresist compositions of the disclosure may further contain asolvent.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the disclosure. The amount ofthe solvent is usually 99.9% by weight or less and preferably 99% byweight or less based on total amount of the photoresist composition ofthe disclosure.

Examples of the solvent include a glycoletherester such asethylcellosolve acetate, methylcellosolve acetate andpropyleneglycolmonomethylether acetate; an ester such as ethyl lactate,butyl acetate, amyl acetate and ethyl pyruvate; a ketone such asacetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; and acyclic ester such as γ-butyrolactone.

The photoresist compositions of the disclosure may further contain aquencher. The “quencher” has the property that it can trap an acid,especially an acid generated from the acid generator by applying aradiation.

Examples of the quencher include a basic nitrogen-containing organiccompound and a salt lower in acidity than an acid generated from theacid generator.

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine and anammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine. Examples of the aromatic amineinclude an aromatic amine in which an aromatic ring has an amino groupsuch as aniline and a heteroaromatic amine such as pyridine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-,3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, dioctylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris [2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenyl methane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy) ethane, di(2-pyridyl)ketone,4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salts include quaternary ammonium salts such astetramethylammoniumhydroxide, tetrabutylammoniumhydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

For the photoresist composition, the salt lower in acidity than an acidgenerated from the acid generator can be selected according to the acidgenerator to be used, examples of which include the salts as shown belowand those as mentioned in JP2012-229206A1, JP2012-6908A1,JP2012-72109A1, JP2011-39502A1 and JP2011-191745A1.

The acidity in the weak acid salt is shown by the acid dissociationconstant (pKa). The acid dissociation constant of acid generated fromthe weak acid salt is usually −3<pKa. The weak acid salt is preferably asalt of −1<pKa<7, and more preferably a salt of 0<pKa<5.

Specific examples of the weak acid salt include the following ones.

Among them, the quencher is preferably a salt represented by formula(D).

The amount of quencher is preferably 0.01 to 5% by mass, more preferably0.01 to 4% by mass, and still more preferably 0.01 to 3% by mass, basedon sum of the solid components.

The photoresist compositions of the disclosure can contain, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the disclosure is not prevented. Thephotoresist compositions of the disclosure can usually be prepared bymixing, in a solvent, resin (A) and an acid generator, and if necessaryresin (Aa), resin (X), a quencher and/or additives at a suitable ratiofor the composition, optionally followed by filtrating the mixture witha filter having 0.003 μm to 0.2 μm of a pore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like.

The mixing time is usually 0.5 to 24 hours, which can be selected inview of the temperature. The means for mixing the components is notlimited to specific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced using the photoresist compositionof the disclosure by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the disclosure ona substrate,

(2) a step of forming a composition film by drying the composition,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Examplesof the substrate include a silicon wafer or other inorganic material.The substrate may be coated with a reflect-preventing layer such as onecontaining hexamethyldisilazane. For forming the reflect-preventinglayer, such composition for organic reflect-preventing layer asavailable on the market can be used.

The composition film is usually formed by heating the coat layer with aheating apparatus such as hot plate or a decompressor, to thereby dryoff the solvent. The heating temperature is preferably 50 to 200° C.,the time of heating is preferably 10 to 180 seconds, and the operationpressure is preferably 1 to 1.0×10⁵ Pa. These conditions can be selectedin view of the solvent.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F2 laser (wavelength: 157 nm),and a light source radiating harmonic laser light in a far UV region ora vacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser). The exposuresource may be electric beam or extremely ultraviolet (EUV).

The step of baking of the exposed composition film is so calledpost-exposure bake, which is conducted with heating means such as hotplates. The temperature of baking of the exposed composition film ispreferably 50 to 200° C., and more preferably 70 to 150° C.

The deprotection reaction further proceeds by post-exposure bake.

The development of the baked composition film is usually carried outwith a developer using a development apparatus. The development methodincludes dipping methods, paddle methods, spray methods and dynamicdispense method. The developing temperature is preferably 5 to 60° C.,and the developing time is preferably 5 to 300 seconds. Photoresistpatterns can be formed by development.

When a positive type photoresist pattern is prepared from thephotoresist composition of the disclosure, the development can beconducted with an alkaline developer. The alkaline developer to be usedmay be any one of various alkaline aqueous solution used in the art.Generally, an aqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the disclosure, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”.

Examples of an organic solvent for organic developer include ketonesolvents such as 2-hexanone, 2-heptanone; glycolether ester solventssuch as propyleneglycolmonomethylether acetate; ester solvents such asbutyl acetate; glycolether solvents such aspropyleneglycolmonomethylether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of organic solvent is preferably from 90% to 100% by weight,more preferably from 95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from50% to 100% by weight, more preferably from 90% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by other solvent than it such as alcohol.

After development, the photoresist film having a photoresist pattern ispreferably washed with a rinse agent. Such agent is not limited tospecific one provided that it dissolve the film to be washed, example ofwhich include a solvent containing a general organic solvent, preferablyalcohol or ester solvents.

After washing, the remained rinse agent on the photoresist film and thesubstrate is preferably removed therefrom.

The photoresist composition of the disclosure is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EB (electronbeam) lithography and EUV exposure lithography, particularly for ArFexcimer laser lithography. The photoresist composition is suitable forthe fine processing of the semiconductor.

EXAMPLES

The photoresist composition of the disclosure will be described morespecifically by Examples, which are not construed to limit the scope ofthe disclosure.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatographyunder the following conditions.

Equipment: HLC-8120GPC type, manufactured by TOSOH CORPORATION

Column: Three of TSKgel Multipore HXL-M with guard column, manufacturedby TOSOH CORPORATION

Solvent: tetrahydrofuran,

Flow rate: 1.0 mL/min.

Detector: RI Detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: standard polystyrene, manufactured by TOSOHCORPORATION.

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.). Here, the values at the peaks of spectrum are referred to as“MASS.”

Example 1

To the reactor, 16.5 parts of the compound represented by formula(I-1-a), 21 parts of the compound represented by formula (I-1-b) and 80parts of methylisobutylketone were added and stirred at 23° C. for 4hours. Then to the obtained mixture, 0.0064 parts of p-toluenesulfonicacid was fed, followed by being stirred at 23° C. for 24 hours. Into themixture, 80 parts of ion-exchanged water were charged and then stirredat 23° C. for 30 minutes, followed by standing the mixture still tocollect a washed organic layer.

The washing process was conducted four times. The obtained organic layerwas concentrated to obtain 30.7 parts of the compound represented by theformula (I-1-c).

To the reactor, 19.8 parts of the compound represented by formula(I-1-c), 10.1 parts of the compound represented by formula (I-1-d) and120 parts of dimethylformamide were added and stirred at 23° C. for 2hours. Then to the obtained mixture, 80 parts of ion-exchanged water and200 parts of ethyl acetate were fed and then stirred at 23° C. for 30minutes, followed by standing the mixture still to collect an organiclayer. Then to the collected organic layer, 60 parts of ion-exchangedwater was fed and then stirred at 23° C. for 30 minutes, followed bystanding the mixture still to collect a washed organic layer. Thewashing process was conducted three times. To the washed organic layerwas concentrated to obtain 17.4 parts of the compound represented by theformula (I-1-e).

To the reactor, 10 parts of the compound represented by formula (I-1-e),50 parts of methanol and 9.2 parts of 10% aqueous potassium hydroxidesolution were added and stirred at 23° C. for 2 hours. Then to theobtained mixture, 1.4 parts of acetic acid was fed and then stirred at23° C. for 30 minutes, followed by being concentrated. To the obtainedconcentrated residues, 20 parts of ethyl acetate and 20 parts ofion-exchanged water were fed and then stirred at 23° C. for 30 minutes,followed by standing the mixture still to collect an organic layer. Thento the collected organic layer, 20 parts of ion-exchanged water was fedand then stirred at 23° C. for 30 minutes, followed by standing themixture still to collect a washed organic layer. The washing process wasconducted three times.

The obtained organic layer was concentrated, followed by separating theobtained concentrates by column chromatography [Column: silica gel 60N(spherical shape, neutral), made by Kanto chemical, Co., Ltd., 100 to210 μm, eluent: n-heptane/ethyl acetate=2/1] to obtain 5.1 parts of thecompound represented by the formula (I-1).

MASS (Mass spectrography): 352.2 (molecular ion peak)

Example 2

To the reactor, 16.5 parts of the compound represented by formula(I-1-a), 23 parts of the compound represented by formula (I-2-b) and 80parts of methylisobutylketone were added and stirred at 23° C. for 4hours. Then to the obtained mixture, 0.0064 parts of p-toluenesulfonicacid was fed, followed by being stirred at 23° C. for 24 hours. Into themixture, 80 parts of ion-exchanged water were charged and then stirredat 23° C. for 30 minutes, followed by standing the mixture still tocollect a washed organic layer. The washing process was conducted fourtimes. The obtained organic layer was concentrated to obtain 24.8 partsof the compound represented by the formula (I-2-c).

To the reactor, 21 parts of the compound represented by formula (I-2-c),10.1 parts of the compound represented by formula (I-1-d) and 120 partsof dimethylformamide were added and stirred at 23° C. for 2 hours. Thento the obtained mixture, 80 parts of ion-exchanged water and 200 partsof ethyl acetate were fed and then stirred at 23° C. for 30 minutes,followed by standing the mixture still to collect an organic layer. Thento the collected organic layer, 60 parts of ion-exchanged water was fedand then stirred at 23° C. for 30 minutes, followed by standing themixture still to collect a washed organic layer. The washing process wasconducted three times. To the washed organic layer was concentrated toobtain 16.8 parts of the compound represented by the formula (I-2-e).

To the reactor, 10.6 parts of the compound represented by formula(I-2-e), 50 parts of methanol and 9.2 parts of 10% aqueous potassiumhydroxide solution were added and stirred at 23° C. for 2 hours. Then tothe obtained mixture, 1.4 parts of acetic acid was fed and then stirredat 23° C. for 30 minutes, followed by being concentrated. To theobtained concentrated residues, 20 parts of ethyl acetate and 20 partsof ion-exchanged water were fed and then stirred at 23° C. for 30minutes, followed by standing the mixture still to collect an organiclayer. Then to the collected organic layer, 20 parts of ion-exchangedwater was fed and then stirred at 23° C. for 30 minutes, followed bystanding the mixture still to collect a washed organic layer. Thewashing process was conducted three times.

The obtained organic layer was concentrated, followed by separating theobtained concentrates by column chromatography [Column: silica gel 60N(spherical shape, neutral), made by Kanto chemical, Co., Ltd., 100 to210 μm, eluent: n-heptane/ethyl acetate=2/1] to obtain 4.2 parts of thecompound represented by the formula (I-2).

MASS (Mass spectrography): 380.2 (molecular ion peak)

Synthesis of Resin

The compounds used in the syntheses of the resin are as follow.

Hereinafter, the compound represented by formula (X), where (X)represents a symbol of the formula, is referred to as “monomer (X)”.

Example 3

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2)and monomer (I-1) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2) andmonomer (I-1)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8800 in 65% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin A1.

Synthesis Example 1

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1) and monomer(a3-4-2) were mixed together with a mole ratio of monomer (a1-1-3),monomer (a1-2-9), monomer (a2-1-1) and monomer (a3-4-2)=35:15:2.5:47.5,and propyleneglycolmonomethylether acetate was added thereto in theamount equal to 1.5 times by mass of the total amount of monomers toobtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) were added as initiators to thesolution in the amounts of 1% by mole and 3% by mole respectively withrespect to the total amount of monomers, and the resultant mixture washeated at 75° C. for about 5 hours. Then, the obtained reaction mixturewas poured into a large amount of a mixture of methanol and water toprecipitate a resin. The obtained resin was filtrated. The obtainedresin was added to a mixture of methanol and water and then repulped,followed by being filtrated to collect washed resin: This washing stepwas conducted twice to obtain the resin having a weight averagemolecular weight of about 8000 in 69% yield. This resin, which had thestructural units of the following formulae, was referred to as ResinAX1.

Synthesis Example 2

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2)and monomer (IX-1) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2) andmonomer (IX-1)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8700 in 60% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin AX2.

Example 4

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (a3-4-2)and monomer (I-1) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (a3-4-2) andmonomer (I-1)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8600 in 62% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin A2.

Example 5

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-3), monomer (a3-4-2)and monomer (I-1) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-9), monomer (a2-1-3), monomer (a3-4-2) andmonomer (I-1)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8500 in 60% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin A3.

Example 6

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2)and monomer (I-2) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-9), monomer (a2-1-1), monomer (a3-4-2) andmonomer (I-2)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8000 in 61% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin A4.

Example 7

Monomer (a1-1-3), monomer (a1-2-9), monomer (a2-1-3), monomer (a3-4-2)and monomer (I-2) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-9), monomer (a2-1-3), monomer (a3-4-2) andmonomer (I-2)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 7900 in 58% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin A5.

Synthesis Example 3

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1) and monomer(a3-4-2) were mixed together with a mole ratio of monomer (a1-1-3),monomer (a1-2-11), monomer (a2-1-1) and monomer (a3-4-2)=35:15:2.5:47.5,and propyleneglycolmonomethylether acetate was added thereto in theamount equal to 1.5 times by mass of the total amount of monomers toobtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) were added as initiators to thesolution in the amounts of 1% by mole and 3% by mole respectively withrespect to the total amount of monomers, and the resultant mixture washeated for about 5 hours at 75° C. Then, the obtained reaction mixturewas poured into a large amount of a mixture of methanol and water toprecipitate a resin. The obtained resin was filtrated. The obtainedresin was added to a mixture of methanol and water and then repulped,followed by being filtrated to collect washed resin: This washing stepwas conducted twice to obtain the resin having a weight averagemolecular weight of about 7900 in 65% yield. This resin, which had thestructural units of the following formulae, was referred to as ResinAX3.

Synthesis Example 4

Monomer (a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (a3-4-2)and monomer (IX-1) were mixed together with a mole ratio of monomer(a1-1-3), monomer (a1-2-11), monomer (a2-1-1), monomer (a3-4-2) andmonomer (IX-1)=35:15:2.5:47.5:5, and propyleneglycolmonomethyletheracetate was added thereto in the amount equal to 1.5 times by mass ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) were addedas initiators to the solution in the amounts of 1% by mole and 3% bymole respectively with respect to the total amount of monomers, and theresultant mixture was heated for about 5 hours at 75° C. Then, theobtained reaction mixture was poured into a large amount of a mixture ofmethanol and water to precipitate a resin. The obtained resin wasfiltrated. The obtained resin was added to a mixture of methanol andwater and then repulped, followed by being filtrated to collect washedresin: This washing step was conducted twice to obtain the resin havinga weight average molecular weight of about 8900 in 60% yield. Thisresin, which had the structural units of the following formulae, wasreferred to as Resin AX4.

Synthesis Example 5

To monomer (a4-1-7), methylisobutylketone was added in the amount equalto 1.5 times by mass of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)were added as initiators to the solution in the amounts of 0.7% by moleand 2.1% by mole respectively with respect to the total amount ofmonomers, and the resultant mixture was heated at 75° C. for about 5hours. Then, the obtained reaction mixture was poured into a largeamount of a mixture of methanol and water to precipitate a resin,followed by being filtrated to obtain the resin having a weight averagemolecular weight of about 18000 in yield 77%. This resin, which had thestructural unit of the following formula, was referred to as Resin X1.

Synthesis Example 6

Monomer (a5-1-1) and monomer (a4-0-12) were mixed together with a moleratio of monomer (a5-1-1) and monomer (a4-0-12)=50:50, andmethylisobutylketone was added thereto in the amount equal to 1.2 timesby mass of the total amount of monomers to obtain a solution.Azobis(2,4-dimethylvaleronitrile) was added as initiator to the solutionin the amount of 3% by mole with respect to the total amount ofmonomers, and the resultant mixture was heated at 70° C. for about 5hours. Then, the obtained reaction mixture was poured into a largeamount of a mixture of methanol and water to precipitate a resin,followed by being filtrated to obtain the resin having a weight averagemolecular weight of about 10000 in yield 91%. This resin, which had thestructural units of the following formulae, was referred to as Resin X2.

<Preparation of Photoresist Composition>

The following components shown in Table 1 were mixed and dissolved,further, filtrated through a fluorine resin filter having pore diameterof 0.2 μm, to prepare photoresist compositions.

TABLE 1 Resin Acid (Kind/ generator No. Parts) (Kind/Parts) PB/PEBComposition 1 X2/0.2 B1-21/0.95 90° C./85° C. A2/10 B1-22/0.4Composition 2 X1/0.2 B1-21/0.95 90° C./85° C. A2/10 B1-22/0.4Composition 3 X2/0.2 B1-21/0.95 90° C./85° C. A1/10 B1-22/0.4Composition 4 X1/0.2 B1-21/0.95 90° C./85° C. A1/10 B1-22/0.4Composition 5 X2/0.2 B1-21/0.95 90° C./85° C. A3/10 B1-22/0.4Composition 6 X2/0.2 B1-21/0.95 90° C./85° C. A4/10 B1-22/0.4Composition 7 X2/0.2 B1-21/0.95 90° C./85° C. A5/10 B1-22/0.4Comparative X2/0.2 B1-21/0.95 90° C./85° C. Composition 1 AX2/10B1-22/0.4 Comparative X2/0.2 B1-21/0.95 90° C./85° C. Composition 2AX4/10 B1-22/0.4 Reference X2/0.2 B1-21/0.95 90° C./85° C. Composition 1AX1/10 B1-22/0.4 Reference X2/0.2 B1-21/0.95 90° C./85° C. Composition 2AX3/10 B1-22/0.4

The symbols shown in Table 1 represent the following components.

<Resin>

A1: Resin A1, A2: Resin A2, A3: Resin A3, A4: Resin A4, A5: Resin A5,AX-1: Resin AX-1, AX-2: Resin AX-2, AX-3: Resin AX-3, AX-4: Resin AX-4,X1: Resin X1, X2: Resin X2

<Acid Generator>

B1-21: Salt represented by formula (B1-21), produced by the methodaccording to JP2012-224611A1

B1-22: Salt represented by formula (B1-22), produced by the methodaccording to JP2012-224611A1

<Solvent>

Mixture of the Following Solvents

Mixture of the following solvents Propyleneglycolmonomethylether acetate265 parts  Propyleneglycolmonomethyl ether 20 parts 2-Heptanone 20 partsγ-butyrolactone 3.5 parts 

(Production of Positive Type Photoresist Patterns)

Silicon wafer (12 inches) was coated with “ARC-29”, which is an organicanti-reflective coating composition available from Nissan ChemicalIndustries, Ltd., and then baked at 205° C. for 60 seconds, to form a 78nm-thick organic anti-reflective coating. One of the photoresistcompositions prepared as above was spin-coated over the anti-reflectivecoating so that the thickness of the resulting film became 85 nm afterdrying.

The silicon wafer thus coated with the photoresist composition wasprebaked on a direct hotplate at a temperature shown in the column “PB”in Table 1 for 60 seconds to form a composition film.

Using an ArF excimer stepper for immersion exposure (“XT: 1900Gi”manufactured by ASML, 3/4 Annular, NA=1.35, XY-pol.) and a mask forpreparing contact hole pattern (hole diameter: 55 nm, hole pitch: 90nm), the wafer having the composition film was subjected to the exposurewith the exposure quantity being varied stepwise.

Ultrapure water was used for immersion solvent.

After the exposure, the wafer was subjected to post-exposure baking on ahotplate at a temperature shown in the column “PEB” in Table 1 for 60seconds and then to to conduct development in the manner of dynamicdispense method for 20 seconds at 23° C. with butyl acetate, product ofTokyo Chemical Industry, Co., Ltd to thereby obtain a negative typephotoresist pattern.

<Evaluation as to Critical Dimension Uniformity (CDU)>

In this evaluation, effective sensitivity was determined as the exposurequantity at which the photoresist pattern having 50 nm of hole diameterwas obtained by the exposure using the above-mentioned mask.

The photoresist patterns having 55 nm of hole diameter were formed bythe same method as described above in which exposure was conducted atthe effective sensitivity.

The hole diameter was measured at 24 points per one hole of the pattern.The average of the values measured as the hole diameter was defined asthe average hole diameter of the hole.

As to the average hole diameter, the standard deviation was obtainedbased on the population which consisted of 400 holes within the samewafer.

The standard deviation whose value was not more than 1.7 nm wasevaluated as “o” (good). The standard deviation whose value was morethan 1.7 nm was evaluated as “X” (bad).

Table 2 illustrates the results thereof. The parenthetical number ineach column of “CDU” represents the standard deviation (nm).

TABLE 2 Ex. No. Composition CDU (nm) Ex. 8 Composition 1 ∘ (1.62) Ex. 9Composition 2 ∘ (1.64) Ex. 10 Composition 3 ∘ (1.64) Ex. 11 Composition4 ∘ (1.65) Ex. 12 Composition 5 ∘ (1.59) Ex. 13 Composition 6 ∘ (1.65)Ex. 14 Composition 7 ∘ (1.60) Comparative Comparative  x (1.89) Ex. 1Composition 1 Comparative Comparative  x (1.85) Ex. 2 Composition 2Reference Reference  x (1.76) Ex. 1 Composition 1 Reference Reference  x(1.74) Ex. 2 Composition 2

The resin of the disclosure can provide a photoresist compositioncapable of forming a photoresist pattern which shows improved criticaldimension uniformity. The compound of the disclosure is useful for amaterial for such resin. The photoresist composition is useful for fineprocessing of semiconductors.

What is claimed is:
 1. A photoresist composition which comprises a resinand an acid generator, wherein the resin comprises a structural unitrepresented by formula (I0), a structural unit represented by formula(a1-1), a structural unit represented by formula (a1-2), a structuralunit represented by formula (a2-1) and a structural unit represented byformula (a3-4):

wherein A¹, A² and A³ each independently represent a C2-C18 divalenthydrocarbon group, R¹, R², R³ and R⁴ each independently represent ahydrogen atom or a C1-C6 saturated hydrocarbon group, X¹ and X² eachindependently represent —O—CO—O— or —O—,

wherein, in formulae (a1-1) and (a1-2), L^(a1) and L^(a2) eachindependently represents an oxygen atom or *—O—(CH₂)_(k1)—CO—O— inwhich * represents a binding site to —CO—, and k1 represents an integerof 1 to 7; R^(a4) and R^(a5) each independently represent a hydrogenatom or a methyl group; R^(a6) and R^(a7) each independently represent aC1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, or acombination of them; m1 represents an integer of 0 to 14; n1 representsan integer of 0 to 10; and n1′ represents 0 to 3,

wherein, in formula (a2-1), R^(a14) represents a hydrogen atom or amethyl group, R^(a15) and R^(a16) each independently represent ahydrogen atom, a methyl group or a hydroxy group, L^(a3) represents anoxygen atom or *—O—(CH₂)_(k2)—CO—O— in which * represents a binding siteto —CO—, and k2 represents an integer of 1 to 7, and o1 represents aninteger of 0 to 10, and

wherein, in formula (a3-4), L^(a7) represents a single bond,*-L^(a8)-O—, *-L^(a8)-CO—, *-L^(a8)-CO—O-L^(a9)-CO—O—, or*-L^(a8)-O—CO-L^(a9)-O—; * represents a binding site to oxygen group,La⁸ and L^(a9) each represent a C1-C6 alkanediyl group, R^(a25) is inoccurrence a carboxyl group, a cyano group or a C1-C4 aliphatichydrocarbon group, R^(a24) represents a hydrogen atom, a halogen atom ora C1-C6 alkyl group optionally having a halogen atom, and w representsan integer of 0 to 8, and wherein the photoresist composition furthercomprises another resin which comprises a structural unit represented byformula (a4-0) and a structural unit represented by formula (a5-1), nostructural unit represented by formula (I0) and no structural unithaving an acid-labile group:

wherein, in the formula (a4-0), R⁵ represents a hydrogen atom or amethyl group, L⁵ represents a single bond or a C1-C4 saturated aliphatichydrocarbon group, L³ represents a C1-C8 perfluoroalkanediyl group, or aC3-C12 perfluorocycloalkanediyl group, and R⁶ represents a hydrogen atomor a fluorine atom,

wherein, in the formula (a5-1), R⁵¹ represents a hydrogen atom or amethyl group; R⁵² represents a C3-C18 alicyclic hydrocarbon group,provided that the alicyclic hydrocarbon group has no substituent on thecarbon atom bonded to L⁵⁵; and L⁵⁵ represents a single bond or a C1-C8alkanediyl group where a methylene group can be replaced by an oxygenatom or carbonyl group.
 2. The photoresist composition according toclaim 1, wherein the content of the structural unit represented byformula (I0) is 2% to 10% by mole relative to all of the structuralunits in the resin.
 3. The photoresist composition according to claim 1,wherein the acid generator comprises a salt represented by formula (B1):

wherein Q¹ and Q² each independently represent a fluorine atom or aC1-C6 perfluoroalkyl group, L^(b1) represents a C1-C24 divalentsaturated hydrocarbon group where a methylene group can be replaced byan oxygen atom or a carbonyl group and where a hydrogen atom can bereplaced by a fluorine atom or a hydroxy group, Y represents a methylgroup where a hydrogen atom can be replaced by a substituent, or aC3-C18 alicyclic hydrocarbon group where a methylene group can bereplaced by an oxygen atom, a sulfonyl group or a carbonyl group andwhere a hydrogen atom can be replaced by a substituent, and Z⁺represents an organic cation.
 4. A process for producing a photoresistpattern comprising the following steps (1) to (5): (1) a step ofapplying the photoresist composition according to claim 1 on asubstrate, (2) a step of forming a composition film by drying thecomposition, (3) a step of exposing the composition film to radiation,(4) a step of baking the exposed composition film, and (5) a step ofdeveloping the baked composition film.